Dual channel actuator controls for fuel metering valves are known in the prior art. In one such control arrangement, a rotary metering valve is enclosed within a valve sleeve whereby the relative angular position of the metering valve and the valve sleeve determines the flow area. The metering valve and the valve sleeve are each positioned by a separate motor such that a main control stepper motor positions the metering valve during normal fuel control operation with an electronic control unit computing the required metered flow. Metering valve position feedback to the electronic control unit is provided by a rotary transducer (e.g., a potentiometer). Upon failure of the electronic control unit the position of the metering valve is frozen and the valve sleeve is positionable by the other motor in response to manual inputs from an operator.
A fuel flow metering system as aforedescribed, while providing for alternative means of fuel metering, does not incorporate electronic control units in each control channel and hence cannot accomplish accurate metering of fuel flow in the event of a failure of the electronic control unit but instead is relegated to manual control of fuel flow with its attendant inaccuracies. Also, in such a system, sleeve and valve position must be known to accurately control fuel flow.